Gyroscopic instrument

ABSTRACT

A gyroscopic instrument having a gyro case including a gyro therein and supported with three degrees of freedom and means for applying a control torque to the gyro about a substantially horizontal axis across the gyro-spin axis at right angles thereto in response to a differentiated value of the inclination of the gyro-spin axis.

United States Patent Inventor Shin-lchi Kawada [56] References Cited A I N Z;Z; E UNITED STATES PATENTS f 1968 1,380,336 5/1921 Paxton 33/226 Patented 2,700,829 2/1955 Statsinger 33/226 A 2,729,107 1/1956 Braddon 74/534 sslgnee Kabushikikakha Tokyo Kelki Selzosho (Tokyo xeikiseimsho Co Ltd) 2,887,783 5/1959 Blizard 33/204X Tokyo Japan 2,968,953 1/1961 Agins 74/S.5 X

9 3 Priority Jam 13 1967 3,443,320 5/1969 Boltmghouse et a1. 33/226 1 FOREIGN PATENTS 42/2649 929,326 6/1955 Germany 33/226 247,265 2/1926 Great Britain 33/226 Primary Examiner-Robert B. Hull Attorney-Hill, Sherman, Meroni, Gross & Simpson GYROSCOPIC INSTRUMENT 6 Claims 7 Drawmg Figs ABSTRACT: A gyroscopic instrument having a gyro case in- U.S. Cl 33/226, eluding a gyro therein and supported with three degrees of 74/55 freedom and means for applying a control torque to the gyro Int. Cl G0lc 19/38 about a substantially horizontal axis across the gyro-spin axis Field of Search 33/226; at right angles thereto in response to a differentiated value of 74/55 the inclination of the gyro-spin axis.

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SHEU 5 OF 5 INVENTOR ///A/ /6/// K AWA DA ;XTTORNEY GYROSCOPIC INSTRUMENT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a gyroscopic instrument for use with ships, airplanes and the like.

2. Description of the Prior Art In prior art an inertial navigation system has been proposed for use with ships, airplanes and the like for detecting and indicating their location, namely azimuth and latitude thereof. However, this conventional system necessitates the use of at least two gyros, two accelerometers, computer, etc., and hence encounters some problems such as expensiveness, complexity in construction and in operation, which impose a severe limitation on wide use of the conventional system at the present stage of the art.

SUMMARY OF THE INVENTION The primary object of this invention is to provide an inexpensive, simply structured, easy to handle and high precision gyroscopic instrument which employs only one gyro but is capable of continuous detection and indication of the azimuth and the latitude on ships, airplanes and the like.

Other objects, features and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic diagram for explaining the principles of this invention;

FIG. 2 is a side view schematically illustrating one example of a gyroscopic instrument produced according to this invention, having one portion removed;

FIG. 3 is a side view schematically illustrating, by way of example, a gyro control signal generator unit and a latitude signal generator unit employed in the gyroscopic instrument ofthis invention, similarly with one portion removed;

FIG. 4 is a connection diagram illustrating electrical connections between a power source and other elements of the gyroscopic instrument of this invention;

FIG. 5 is a side view schematically illustrating another example of the gyroscopic instrument of this invention, having one portion removed;

FIGS. 6 and 7 are side views schematically illustrating other examples ofthe gyro control device ofthis invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings the present invention will be described in detail. In FIG. I illustrating the principle of this invention, reference numeral 4 indicates a gyro case having incorporated therein a gyro (not shown), which case is mounted on a support base 10 by means described later. The gyro is positioned in the gyro case 4 at its center 0 concentrically therewith and is driven at high speed. The vector of the angular momentum of the gyro is indicated by an arrow H. Let it be assumed in this case that the gyro rotates in such a manner that a right-hand screw is driven from the center 0 in the direction indicated by the arrow H. The gyro case 4 has attached thereto shafts 5 and 5 crossing the spin axis ofthe gyro at right angles thereto, and free ends of the shafts 5 and 5' are supported by a vertical ring 6 to permit rotation of the gyro case 4 about the axis of the shafts 5 and 5'. It is to be realized that in this specification the reference to ring 6 being vertical refers to the analogy with leveled gyros. The shafts 5 and 5 are tilted with ring 6. The ring 6 in its settled condition has its central axis parallel to the axis of the earth.

The vertical ring 6 has horizontal shafts 7 and 7' perpendicular to the shafts 5 and 5, the shafts 7 and 7' being supported at one end by an outer ring 8, (which is shown in a substantially U shaped configuration in FIG. 1). In this case, the vertical ring 6 is freely rotatable about the shafts 7 and 7' rela tive to the outer ring 8, which is, in turn, mounted on the sup port base 10 directly or through any support member.

Such an instrument as described above might be generally called a three-degree-of-freedom gyroscope G, if no friction should be yielded about the shafts 5 and 5', 7 and 7. Unless applied to a torque from the outside, its angular momentum remains constant and the direction of the gyro-spin axis, that is, the direction of the vector H of the angular momentum in FIG. 1 is invariable relative to absolute space in accordance with Newtons law of conservation of angular momentum. Now, a straight line is drawn from the center 0 of the gyro in the direction of the arrow H, which is identified at reference character a. Another straight line ON is drawn through the center 0 of the gyro in a horizontal plane in parallel relation to the meridian, and a desired point B is taken in the line ON. Then, two points E and W are taken in a straight line b which intersects with the line ON at right angles thereto at the point B in the horizontal plane. In addition, straight lines c and d are respectively drawn upward from the points E and W in a vertical direction and points E and W are takep in the straight lines c and d in such a manner that segment E'W'joining the two points may be parallel with EW. The point at which the straight line a crosses a plane EWE'W' thus obtained, is identified by S. Further, a perpendicular is drawn from the point S to the segment EW and its foot is denoted A. As depicted in the figure, an angle defined by the segment (TA joining the center 0 of the gyro case 4 and the point A and the segment OS is referred to as 6, while an angle defined by a segment OEjoining the center 0 of the gyro case 4 and the point B on the straight line ON and the segment M is referred to as I In such a case, if the place where the gyro is located is not of high latitude, the aforementioned point S travels on the plane EWWE' as indicated by the dotted line i with the lapse of time for the following reason. That is, the segment O S agrees with the direction of the gyro-spin axis and hence is invariable relative to absolute space, while the plane EWW'E' is fixed on the earth and hence rotates with the earth. This causes such a circular movement of the point S as indicated by the dotted line i. If now a straight line 2 is drawn from the center 0 of the gyro case 4 in parallel relation to the axis of the earths rotation and its intersecting point with the plane EWW'E' is denoted P, the point P naturally lies in a straight line fwhich is perpendicular to the straight line EW on the plane EWWE' and an angle BOP agrees with the latitude of the place where the gyro is situated. As mentioned above, the direction of the segment OS is in agreement with that of the gyro spin axis and hence is invariable with respect to absolute space. While, if the plane EWW'E' is on the earth, it shifts with the rotation of the earth with respect to absolute space. Therefore, the segmentOSperforms conical motion about the point 0, and accordingly the locus of the point S on the plane EWWE' forms an ellipse. In this case the point S moves about the point P while maintaining the angle SOP constant, and the period of the circular motion of the point S is approximately 24 hours. The locus of the point S is indicated by the dotted line i.

In the above-described system the use ofa device capable of controlling the gyro continuously to hold the point S at the point P could provide continuous and accurate detection of the latitude and the direction of the meridian at any desired place on the earths surfaceb measuring the angle POB and the direction of the segment OB.

The present invention resides in the concept to simultaneous measurement of true north and latitude through the use of a single gyro by utilizing the property of the gyro and in the development of the techniques for embodiment of the con cept.

A description will hereinbelow be given of the concept on which this invention is based. This invention is to control the gyro in a manner quite different from that of the conventional gyrocompasses, as will be described later, based upon the fact that while the point S is biased further to the cast (in the direction ofthe segment ET? in FIG. 1) than the straight linef WW) than the line fthe angle 9 goes on decreasing. The control operations for the gyro in this invention include (i) detecting a differentiated value 6 of the angle (or the rate of 6) and (ii) applying a torque substantially proportional to the differentiated value 6 to the gyro about the horizontal axis thereof, namely about the shafts 7 and 7'. In this case, while the differentiated value ti is positive, that is, while the angle 0 increases, the control torque is applied to the gyro about the shafts 7 and 7 in such a direction that the gyro-spin axis precesses to cause a decrease in I3, that is, in the angle BOA. While the differentiated value 0 is negative, the angle 0 decreases, the control torque is applied to the gyro in such a direction that the gyro-spin axis precesses in a direction opposite to the above-mentioned one. Now the above operations will be described more in detail. In the first place, the differentiated value 0 of the angle 0 is detected, and while (7 remains positive, the point S lies further to the east than the linef, as will be apparent from the foregoing. In this case, ifa torque of such a direction that a right-hand screw is driven from the point 0 in the direction of the shaft 7, is applied to the gyro about its horizontal shafts 7 and 7, the precession caused in the gyro tends to direct the point S to the straight linef, that is, in a direction indicated by arrows a,in FIG. 1. As a result of this, the point S does not move on its locus indicated by the dotted line i which is formed when the gyro is not controlled, and instead the point S draws a locus more direct toward the linef, That is, the point S moves on a locus such as indicated by 1,. Further, when the point S passes across the linefit is to turn about the point P while at the same time descending under the influence of the rotation of the earth. However, simultaneously with the descent of the point S, a torque substantially proportional to the differentiated value 6 begins to act about the horizontal shafts 7 and 7' in such a direction that a right-hand screw is driven from the shaft 7 in the direction of the point 0. This produces precession in the gyro, by which the point S is caused to approach again the linef, in a direction indicated by arrows a in FIG. l.

Where the gyro is not constrained, that point S accomplishes nonattenuated periodic motion, that is, periodically moves on the dotted line i. In the present invention a torque substantially proportional to the differentiated value 6 is applied to the gyro about its horizontal shafts 7 and 7' in the aforementioned direction, as above described, so that the point S finally comes to agree with the point P following the spiral locus i of the attenuated periodic motion. If the torque is substantially or exactly proportional to Q the attenuated periodic motion becomes gradually nonoscillatory and finally becomes as indicated by a full line i so that the point S may reach the point P in a substantially straight line. Thus, even if periodic motion having a period of 24 hours is initiated with the point S selected at any desired point, the point S can be brought to the point P within several hours.

With the gyro of this system, the latitude and the meridian can be simultaneously detected and indicated by the angle P013 and the straight line OB respectively.

A description will hereinafter be made in connection with one example of an instrument embodying the principles of this invention. In FIG. 2 there is illustrated, partly in cross section, one embodiment of this invention. A container 8 has incorporated therein a vertical ring 6 having horizontal shafts 7 and 7', which are supported on the container 8' through ball bearings B and B. The vertical ring 6 has supported therein by ball bearings B, and B, a spherical gyro case having vertical shafts and 5. The gyro case 4 has housed therein a gyro (not shown) which is driven at high speed as in FIG. 1, and in FIG. 2 the gyrospin axis is normal to the plane of the paper. FIG. 2 illustrates an example in which the vertical shafts 5 and 5 are vertical.

The container 8 has projected outside thereof shafts 11 and 11 coaxially with the horizontal shafts 7 and 7', and the shafts 11 and 11 are supported by a horizontal ring 12 by means of ball bearings 8 and B The horizontal ring 12 has attached thereto shafts 31 and 31' (not shown) at right angles to the shafts 11 and 11 and normal to the sheet, which shafts 31 and 31' are, in turn, supported by a follower ring 13 by means of ball bearings (not shown). The follower ring 13 has secured thereto at upper and lower portions shafts 9 and 9, which are attached to a support 14 through ball bearings B and B so that the follower ring 13 is supported by the support 14. The support 14 is fixed on a support base 10 on which a binnacle 15 is mounted. At the top of the binnacle 15 there is formed a window into which a glass 30 is fitted. Further, the shaft 9' has mounted thereon a compass card 29 by suitable means, and a pointer 28 is fixedly mounted on the support 14 in such a manner that an azimuth scale on the compass card 29 can be read out relative to the pointer 28. In addition, an azimuth gear 22 is secured to the follower ring 13 near its lower end, which gear constitutes a gear train together with gears 23 and 24 and a pinion 25. The gear train is rotated by a servomotor 26 having the pinion 25. A weight 21 is attached to the container 8' at its lower portion to ensure that even if, for example, a ship equipped with the present instrument lists, the container 8 does not turn over and is controlled by the degree of freedom of the shafts 11, 11', 31 and 31' so that the weight 21 is always directed downwards due to gravity acting thereon.

The container 8' is filled with a liquid 32' such as transformer oil or-the like and the gyro case 4 is designated so that its specific gravity is substantially equal to that of the liquid 32'. This ensures that the shafts 5 and 5 do not render any load to the ball bearings supporting them, and consequently friction of the bearings can be regarded as negligibly small in practice. Further, the entire specific gravity of the vertical ring 6 and the horizontal shafts 7 and 7 formed integrally therewith can also be selected exactly or nearly equal to that of the liquid 32, by which friction of the ball bearings supporting the shafts 7 and 7' can also be reduced to a small value.

The relative angular deviation between the gyro case 4 and the vertical ring 6 is detected by means ofa deviation detector 18 which consists of deviation detector elements 18 and 18" cooperating with each other, the former being mounted on the vertical ring 6 and the latter on the gyro case 4 at a position corresponding to the former. The deviation detector 18 may be in theform of, for example, a differential transformer, which is suitable for use in this case. An electric signal proportional to a deviation between the gyro case 4 and the vertical ring 6, detected by the deviation detector 18, is fed through an amplifier (not shown) to a servomotor 26 to rotate it. The rotation of the servomotor 26 is transmitted through the gears 25, 24 23 and 22 to the follower ring 13 to drive it about the shafts 9 and 9'. This rotates the vertical ring 6 about the shafts 5 and 5' through the shafts 31 and 31', the horizontal ring 12, the shafts 11 and 11', the container 8' and the shafts 7 and 7' to control the vertical ring 6 in such a manner as to be always in agreement with the gyro case 4 without producing any relative deviation therebetween. That is, the relative deviation detector 18, the amplifier, the servomotor 26, the gear train 25, 24, 23 and 22, the support rings 13, 12, the container 8' and the vertical ring 6 constitute one servosystem. With such an arrangement, the shafts 5 and 5', the horizontal shafts 7 and 7' and the gyro-spin axis always intersect at right angles to one another, providing the gyro with three degrees of freedom. At the same time, the azimuth of the gyro can be read out from the compass card 29 mounted on the shaft 9' relative to the pointer 28 secured to the support 14.

Meanwhile, a rotor 17 is fixedly mounted on the shaft 7 and a stator 17" is disposed on the container 8, which rotor and stator interact in a manner to constitute a torquer 17. The torquer 17 serves to apply to the gyro about the shafts 7 and 7 a torque in proportion to the aforementioned differentiated value 9, and in practice any type of conventional torquer may be employed in this invention. The torquer 17 exemplified in FIG. 2 is an induction-type torquer in which the rotor 17' is a metal cylinder and the stator 17 is an E-shapd laminated core with windings wound on its three legs.

Reference numeral 16 indicated generally a device for effecting detection of (I necessary for the gyro control system of this invention and for detection of the latitude. In the illustrated example, the device 16 is shaped in a cylindrical configuration which has incorporated therein a servomotor, gears, a synchro generator and an electrolyte level and is mounted about the shaft 7'. Referring now to FIGS. 3 and 4, a descrip tion will be given of the construction of the device 16 and the torquer I7, prior to describing the operation of the instrument of this invention depicted in FIG. 2. FIG. 3 is a schematic dia gram of the device 16 viewed from the axial direction of the shaft 7', in which a cylindrical case 32 of the device 16 is mounted about the shaft 7' by means of ball bearings 47 and 47' disposed centrally of end faces of the case 32. That is, the case 32 is rotatable about the shaft 7'. Further, a gravity reference such, for example, as an electrolyte level 33 is secured to the case 32 by means of, for example, bolts R,, as illustrated, and a servomotor 35, a precision synchro generator 48 and an intermediate gear train 59 are respectively fixed to the case 32. The free end of a rotary shaft 35' of the servomotor 35 has mounted thereon a worm 53, which is, in turn, engaged with the intermediate gear train 59. The rotation of the servomotor 3S reduced by the gear train 59 is transmitted therethrough to a spur gear 54 mounted on the shaft 7'. Rotation of the rotary shaft 35 of the servomotor 35 leads to rota tion of the case 32 about the shaft 7. The synchro generator 48 is adapted so that its shaft is rotated by a gear engaged with the spur gear 54 or by a gear engaged with the gear train consisting of the worm 53, the intermediate gear 59 and the spur gear 54. In FIG. 4 there is depicted a connection diagram of the gyroscopic instrument of this invention exemplified in FIGS. 2 and 3. In other words, FIG. 4 is a correction diagram for the purpose of describing the operations of the electrolyte level 33, the servomotor 35, and the torquer 17. These elements will hereinbelow be described in detail. The electrolyte level 33 is such that an electrolyte 52 is enclosed in a sealed glass vessel having a similar curvature to that of a conventional spirit level and a bubble B is formed in the vessel, as depicted in the figure, and electrodes 49, 50 and 51 are disposed in the sealed glass vessel. Reference numeral 42 designates a transformer consisting of a primary winding 41 and two secondary windings 39 and 40. The primary winding 41 is connected to an AC power source 46, so that AC currents of low voltage of the same value are applied from the secondary windings 39 and to the electrodes and 51 of the electrolyte level 33. The polarities of the two secondary windings 39 and 40 are determined as indicated by dots in the figure. Where the electrolyte level 33 is horizontal and accordingly the bubble B rests at the center of the vessel (at a neutral position the electrical resistance values of the electrolyte present between the electrodes 49 and 50 and between the electrodes 49 and 51 are equal to each other, so that no voltage is produced between a terminal 55 and the electrode 49. When the electrolyte level 33 is inclined and consequently the bubble ,8 shifts from the center of the vessel, there is produced a difference in the electrical resistance values of the electrolyte between the electrodes 49 and 50 and between the electrodes 49 and 51. This produces a voltage between the terminal 55 and the electrode 49, which voltage is amplified by an amplifier 34 and shifted about 90 in phase, thereafter being applied to a control winding 36 of the servomotor 35. An energizing winding 37 of the servomotor 35 is energized by the AC power source 46 and the servomotor 35 is a two-phase induction motor in principle, so that application of the aforementioned control voltage to the control winding 36 leads to rotation of the servomotor 35.

Assume that the gyro case 4 is pointing to the point S as depicted in FIG. I and the electrolyte level 33 is horizontal. Thereafter, the gyro changes its position along the dotted line i of FIG. I due to the rotation of the earth, with the result that the angle 0 in FIG. 1 gradually increases. The change produces rotation of the vertical ring 6 with and about the axis of shafts 7 and 7', while the shaft 7 and the case 32 are engaged by the worm 53 and hence are initially rotated together. As a result of this, the electrolyte level 33 gradually inclines with an increase in the angle 9. This inclination is detected in the form of movement of the bubble B, and consequently an AC signal is produced between the terminal 55 and the electrode 49 as described above, which signal is fed through the amplifier 34 to the control winding 36 of the servomotor 35. With the feeding of the signal to the control winding 36, the servomotor 35 begins to rotate to drive the case 32 relative to shaft 7 in a manner to hold the electrolyte level in a horizontal position, thus maintaining the device 16 substantially invariable relative to the earth. That is, the device 16 is a servosystem by means of which the electrolyte level 33 is rotated about the shaft 7' in response to the change of the position of the gyro relative to the earth so as to ensure that the electrolyte level 33 is controlled to always lie in a horizontal position. Accordingly, the rotational speed of the servomotor 35 is in proportion to the differentiated value 6 of the angle 6 and the rotational speed of the servomotor 35 is also substantially proportionate to the voltage of the control phase, so that the output voltage of the amplifier 34 is also substantially proportional to the differentiated value 0 Briefly stated, when the position of the gyro changes relative to the earth and the angle 6 varies correspondingly, if the rotational speed of the servomotor 35 is lower than an optimum speed, the difference between the position of the bubble B and its neutral position is naturally caused to gradually increase for the following reason. The rotation of the case 32 about the shaft 7 cannot follow the rotation of the shaft 7' because the speed of the servomotor is too low, with the result that the case 32 gradually inclines together with the gyro in a manner to cause an increase in the angle 0. In this case, the bubble [3 goes away from its neutral position more and more and the output of the amplifier 34 in creases to control the servomotor 35 in such a manner as to drive it more rapidly. As a result of this, the servomotor finally comes to be driven at an optimum speed in agreement with the differentiated value 0 of the angle 0. In other words, proportional relationship is constituted between the rotational speed of the servomotor and the value 0 and between the output of the amplifier 34 and 0.

Therefore, the principles of this invention can be embodied merely by applying to the gyro about the horizontal shafts 7 and 7' through the torquer 17 the torque proportional to the output of the amplifier 34 which is, in turn, proportional to 6 In the example shown in FIG. 4, the output of the amplifier 34 is fed to a winding 43 wound on the central leg of the E-shaped core of the stator 17", and windings 44 and 45 on the other two legs are energized by the AC power source 46. In such a case, if the rotor 17' takes the form of, for instance, a cylindrical metal conductor, the stator 17" can apply to the rotor 17 a reversible torque proportional to the output voltage of the amplifier 34 by the principle of the two-phase motor.

Thus, when a torque proportional to 9 is applied to the gyro about the horizontal shafts 7 and 7, the instrument depicted in FIG. 2 should move toward and settle in a position pointing to the point P of FIG. 1 in accordance with the principles above described with FIG. 1. Further, since the elements disposed within the container 8 are free from error-producing conditions by rolling and/or pitching of, for example, a ship due to degrees of freedom of the shafts 11, ll, 31 and 31', the above-described purposes can be accomplished by the present invention instrument on the ship.

The rotor of the synchro generator 48, though not shown, is so arranged as to be rotated in proportion to the relative rotational angle between the shaft 7' and the case 32, so that, on the basis of the position of the rotor of the synchro generator 48 when the gyro-spin axis and the electrolyte level are horizontal, the angle indicated by the synchro generator 48 when the gyro-spin axis has come to rest toward the point P in FIG. I is representative of the latitude itself. That is, the latitude can be always continuously indicated by a synchro receiver connected to the synchro generator 48. It is of course possible to replace the synchro device with a potentiometer or a two-speed synchro system.

The azimuth can readily be read out from the compass card 29 relative to the pointer 28. Further, even if the latitude varies with advancement of the ship after the point P has been once indicated, the angle is always representative nf the latitude of the ships location, and hence the absgflute value of the ship's speed in the north-south direction can be obtained from the differentiated value 0 of the angle 6.

The gyroscopic instrument of this invention adapted for simultaneous indication of latitude and azimuth can be provided with a repeater generator mechanism 64, a repeater, an alarm, etc. in a similar manner to conventional types of gyrocompasses.

The 6 detecting means depicted in FIG. 3 is a mere example thereof and it is needless to say that the electrolyte level 33 ex emplified in the figure can be replaced by any of various accelerometers developed for use with the inertial navigation system. In case of using an accelerometer having a wide acceleration-detecting range, it is directly secured to the vertical ring 6 without employing the servosystem including the servomotor 35, by which an output is led out in proportion to the angle 0 and the resulting output is differentiated by a known computer to provide 0 Although the method described with FIGS. 3 and 4 consists in the detection of 9 by the use of the device I6 and in the application of a torque to the gyro through the torquer 17 in response to f), the reference to this method should not be construed as limiting this invention specifically thereto. In short, the purpose can be accomplished by the employment of any means capable of producing a torque about the horizontal shafts of the gyro in proportion to 0 FIG. 6 illustrates another example of the method for serving the purpose, which employs the device 16 depicted in FIG. 3 and in which a weight 65 is mounted on the case 32. This is a method based upon the fact that the followup error of the servosystem including the electrolyte level 33, the amplifier 34, the servomotor 35 and the gear trains 53, 59 and 54 is substantially proportional to 6 The case 32 deviates from its neutral position in response to the followup error and the weight 65 shifts to right or left correspondingly to produce a restoring torque due to gravity acting upon the weight 65, which torque is substantially proportional to 9. Accordingly, in this case the torquer 17 is unnecessary. In the case of the system of FIG. 6, the servosystem from the electrolyte level 33 to the gear 54 must be designed to be high precision and provide a suitable followup error proportional to the speed of the servomotor.

FIG. 7 illustrated still another example of the method for serving the above purposes which also utilizes substantial proportionality of the angular error of the servosystem to t) and in which the interior construction of the case 32 is exactly the same as that of the case depicted in FIG. 6, except that the weight 65 is replaced with two pots 66 and 67 interconnected at upper and lower end faces thereof by an air pipe 68 and a communicating pipe 69. The pots 66 and 67 and the communicating pipe 69 enclose therein a liquid, for example, mercury in such an amount as to fill about half the pots when the case 32 rests at its neutral position when the bubble B of the electrolyte level 33 lies at the center of its vessel. With such a device, when an angular error is produced in the servosystem the liquid flows into a lowered pot from the elevated one, since the liquid levels in the two pots are always held in the same horizontal plane in the field of gravity by the syphon principle. This yields a torque about the shafts 7 and 7 which tends to push down the lowered pot. The torque is in proportion to the servo error and the latter is, in turn, substantially proportional to 0 so that the torque is naturally in proportion to d. The device exemplified in FIG. 7 is advantageous in that the torquer 17 can similarly be dispensed with as in the case of FIG. 6 and in that the proportionality constant of the torque substantially proportional to d can be made maximum by increasing the cross-sectional area of the pots 66 and 67. In this example, however, since the torque is produced in an opposite direction to that in FIG. 6, it is necessary to reverse the direction of the vector H of the angular momentum of the gyro, that is to rotate the gyro in a reverse direction.

As has been described in the foregoing, there are many means for detecting (i, all of which can be employed in this invention so long as they are adapted to apply a torque to the gyro about its horizontal shafts substantially in proportion to Similarly, in the example shown in FIG. 4 it is needless to say that the servomotor 35 and the torquer 17 may be respectively controlled by individual amplifiers without applying the same output of the single amplifier 34 to the servomotor 35 and the torquer I7.

In FIG, 5 there is illustrated another example of the gyroscopic instrument which is quite different from that depicted in FIG. 2 in the construction of the support mechanism. That is, the container 8' is exactly the same in the interior construction as that of FIG. 2 but is supported in a quite different manner. In the example of FIG. 5 the container 8' has directly attached thereto follower shafts 9 and 9', which are, in turn, supported by a vertical outer ring 60 by means of bearings (not shown). The vertical outer ring 60 has gimbal shafts 611 and 611' (not shown) and are supported by a gimbal ring 62 through bearings. In addition, the instrument is designed so that the center of total gravity of the components disposed within the vertical outer ring 60 lies under the shaft 61. The gimbal ring 62 is provided with horizontal gimbal shafts 63 and 63' (not shown) arranged at right angles to the gimbal shaft 61, and the shafts 63 and 63 are, in turn, supported by a binnacle (not shown). With such an arrangement, even if the binnacle inclines with a ship, the shafts 9 and 9' are held substantially vertical due to degrees of freedom of the shafts 61, 61', 63 and 63' and due to gravity and hence shafts 9 and 9' are not directly affected by the oscillatory motion of the ship.

A description will hereinbelow be made in connection with novel means for improving the performance of the gyroscopic instrument which forms one important part of this invention. As illustrated in FIG. 4, a rotor 17, and a stator 17,", identical in construction with the aforementioned ones 17' and 17'', are mounted about the vertical shaft 5 or 5' in a manner to constitute a torquer l7, and a circuit is additionally provided for energizing a control winding of the torquer I 1 similar to the winding 43 in proportion to the output of the amplifier 34. In this case the other elements of the gyroscopic instrument such as those of the device 16 and so on are exactly the same as the aforementioned ones of the instrument illustrated in FIG. 4. Providing that the point S stays on the right side of the linefin FIG. 1 and the angle 6 gradually increases, a torque is applied to the gyro about the vertical shaft 5 or 5' in propor tion to its differentiated value 0 thereby to urge an increase in 9. In other words, this method leads to shortening of the period of the gyro motion. Accordingly, by suitably selecting the proportionality constant of the torque applied to the gyro about its vertical shaft 5 or 5 substantially in proportion to (i, the point S located at any desired place in FIG. 1 can be brought to the point P more rapidly than in the case Where the above means are not provided.

As is apparent from the foregoing, the present invention is to provide a gyroscopic instrument for use with airplanes, ships and the like which employs only one gyro but is capable of not only providing the reference of azimuth as a gyrocom pass but also continuous detection and indication of the latitude corresponding to a place where the instrument is located.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of this invention.

I claim as my invention:

I. A gyroscopic instrument comprising a gyro case having incorporated therein a gyro, means for supporting said gyro case with three degrees offreedom, means for producing a differentiated value of inclination of the spin axis of said gyro with respect to a substantially horizontal axis across said spin axis and at right angles thereto and for producing an electrical signal corresponding to said differentiated value of inclination, means receiving said electrical signal to produce a control torque dependent upon only said differentiated value of inclination and for applying said control torque to said gyro case about said substantially horizontal axis, whereby said spin axis of said gyro processes about an axis parallel to the axis of the earth with a period of not greater than about 24 hours with respect to the earth, said precession being damped in accordance with time lapse, and said spin axis settles in a position parallel to the axis of the earth.

2. A gyroscopic instrument as claimed in claim 1 in which said second-mentioned means consists of a gravity reference, a servomotor mounted on said case, a horizontal shaft rotatable about said horizontal axis with said gyro case, a gear fixed to said shaft, a gear train for connecting said gear to a shaft of said servomotor, an amplifier means for amplifying an electrical signal from said gravity reference and applying said amplified electrical signal to said servomotor to control it.

3. A gyroscopic instrument as claimed in claim 1, wherein said first-mentionedmeans consists of a pair of vertical shafts mounted on one of a pair of horizontal shafts attached to a vertical ring for supporting a pair of vertical shafts attached to said gyro case and a stator mounted in a container for supporting said horizontal shafts.

5. A gyroscopic instrument as claimed in claim 1 further comprises a second means for receiving said electrical signal to produce a second control torque dependent upon said differentiated value of inclination and for applying said second control torque to said gyro case about an axis perpendicular to both of said horizontal axis and said spin axis in such a direction as to increase the differentiated value of inclination with respect to said. gyro case, whereby said spin axis of said gyro precesses about an axis parallel to the axis of the earth with a period shorter than 24 hours.

6. A gyroscopic instrument as claimed in claim 5 in which said second-mentioned means consists of a gravity reference, a case for supporting said gravity reference, a servomotor mounted on said case, a horizontal shaft rotatable about said horizontal axis with said gyro case, a gear fixed to said shaft, a gear train for connecting said gear to a shaft of said servomotor, an amplifier means for amplifying an electrical signal from said gravity reference and applying said amplified electrical signal to said servomotor to control it. 

1. A gyroscopic instrument comprising a gyro case having incorporated therein a gyro, means for supporting said gyro case with three degrees of freedom, means for producing a differentiated value of inclination of the spin axis of said gyro with respect to a substantially horizontal axis across said spin axis and at right angles thereto and for producing an electrical signal corresponding to said differentiated value of inclination, means receiving said electrical signal to produce a control torque dependent upon only said differentiated value of inclination and for applying said control torque to said gyro case about said substantially horizontal axis, whereby said spin axis of said gyro processes about an axis parallel to the axis of the earth with a period of not greater than about 24 hours with respect to the earth, said precession being damped in accordance with time lapse, and said spin axis settles in a position parallel to the axis of the earth.
 2. A gyroscopic instrument as claimed in claim 1 in which said second-mentioned means consists of a gravity reference, a servomotor mounted on said case, a horizontal shaft rotatable about said horizontal axis with said gyro case, a gear fixed to said shaft, a gear train for connecting said gear to a shaft of said servomotor, an amplifier means for amplifying an electrical signal from said gravity reference and applying said amplified electrical signal to said servomotor to control it.
 3. A gyroscopic instrument as claimed in claim 1, wherein said first-mentioned means consists of a pair of vertical shafts attached to said gyro case, a vertical ring for rotatably supporting said pair of vertical shafts, a pair of horizontal shafts with first ends attached to said vertical ring and a container for rotatably supporting said horizontal shafts at other ends, respectively.
 4. A gyroscopic instrument as claimed in claim 1 wherein said third-mentioned means is a torquer consisting of a rotor mounted on one of a pair of horizontal shafts attached to a vertical ring for supporting a pair of vertical shafts attached to said gyro case and a stator mounted in a container for supporting said horizontal shafts.
 5. A gyroscopic instrument as claimed in claim 1 further comprises a second means for receiving said electrical signal to produce a second control torque dependent upon said differentiated value of inclination and for applying said second control torque to said gyro case about an axis perpendicular to both of said horizontal axis and said spin axis in such a direction as to increase the differentiated value of inclination with respect to said gyro case, whereby said spin axis of said gyro precesses about an axis parallel to the axis of the earth with a period shorter than 24 hours.
 6. A gyroscopic instrument as claimed in claim 5 in which said second-mentioned means consists of a gravity reference, a case for supporting said gravity reference, a servomotor mounted on said case, a horizontal shaft rotatable about said horizontal axis with said gyro case, a gear fixed to said shaft, a gear train for connecting said gear to a shaft of said servomotor, an amplifier means for amplifying an electrical signal from said gravity reference and applying said amplified electrical signal to said servomotor to control it. 